3 - Is the pest already listed in a PM4 standard on the concerned host plant?

No

Conclusion:

Evaluation continues

4 - Are the listed plants for planting the main* pathway for the "pest/host/intended use" combination? (*: significant compared to others):

Yes

Conclusion:

Candidate

Justification:

Ustilago tritici (U. segetum var. tritici) causes loose smut of wheat. Infection is seed-borne within the seed. The spores of Ustilago tritici germinate on the ovary of a flowering plant and hyphae penetrate the ovary wall and grow towards the developing scutellum and embryo and remain dormant in these tissues until the seed starts to germinate. Seed is therefore a pathway. Infected seeds give rise to systemically infected plants and diseased ears are visible directly after heading. The black spores are released between glumes and broken-down grains, and are blown by the wind to infect neighbouring healthy ears (EPPO, 1997). Seed certification and seed treatment are very effective in controlling the disease, which is now practically unknown in intensive cereal cultivation in Europe. If untreated farmer-saved seed is sown, however, these diseases reappear (EPPO, 1997).
The directive 66/402 has a requirement for the seed producing crop that Ustilaginaceae shall be at the lowest possible level, but no seed-testing requirements are given. There is not a seed test by embryo extraction described by ISTA.
Volunteer plants grown from spilt contaminated seed from the previous year could in theory act as a disease source but this appears to be very rare because no references to this could be found. It is concluded seed can be considered as a significant pathway for the pest.

5 - Economic impact:

Are there documented reports of any economic impact on the host?

Yes

Justification:

In Canada, the percentage of common bread wheat (T. aestivum) fields affected varied from 6% in 1989 to 36% in 1995 with means of 0.1% or fewer infected plants. Durum wheats (T. durum) are generally more susceptible and the percentage of fields affected varied from 45% in 1994 to 78% in 1995, with the mean level of infected durum wheat plants per field ranging from <0.1 to 0.4%. (Thomas and Menzies, 1997). Loose smut disease of wheat in Canada, caused by Ustilago tritici, causes significant economic losses on both durum and bread wheats (Randhawa et al., 2009).
In the UK on T. aestivum it has been rare since the 1970's appearing to be related to more resistant varieites and possibly widespread use of dwarfing genes. The risk of in-crop losses is given as low if grown from certified seed and high if seed saved repeatedly without treatment, and the risk to adjacent crops is moderate only if kept as seed (Paveley et al., 1996).

What is the likely economic impact of the pest irrespective of its infestation source in the absence of phytosanitary measures? (= official measures)

Medium

Is the economic impact due to the presence of the pest on the named host plant for planting, acceptable to the propagation and end user sectors concerned?

No

Conclusion:

Candidate

Justification:

Yield losses are in proportion to the percentage of infected heads in the crop. Generally losses are low 1% but can be as high as 30%. Teliospores from infected ears can infect ovaries of health plants, re-establishing the disease in the next generation of seed produced. Infected seed are otherwise normal, visibly unaltered and fully germinable (Compendium of wheat diseases and pests, 2010). Potential for the disease to multiply within a few years is great if seed is sown untreated or without a systemic seed treatment.

6 - Are there feasible and effective measures available to prevent the presence of the pest on the plants for planting at an incidence above a certain threshold (including zero) to avoid an unacceptable economic impact as regards the relevant host plants?

Yes

Conclusion:

candidate

Justification:

Control through standards for field inspection and seed, use of less susceptible varieties, and mostly through systemic seed treatment fungicides (e.g. tebuconazole, triticonazole, prothioconazole). These fungicides are not allowable for organic farming (management through testing and field inspections).

7- Is the quality of the data sufficient to recommend the pest to be listed as a RNQP?

Yes

Conclusion:

Candidate

Justification:

CONCLUSION ON THE STATUS:

Recommended for listing as an RNQP, based on data.

8 - Tolerance level:

Is there a need to change the Tolerance level:

Yes

Proposed Tolerance levels:

A tolerance (0.1% of seeds infected) for Pre-basic and Basic material (alternative option: absence of symptoms in the crop and its immediate vicinity), a tolerance (0.5 to 2% of seeds infected – no consensus within the SEWG) for certified material, with alternative risk management measures.

Justification (if necessary):

Relative importance of field inspection and sample testing was discussed by the SEWG. The SEWG agreed that field inspection, for this pest, will only show the level of presence of the pest in the planted material and not in the final seed lot. The SEWG agreed with the definition of a threshold for seeds and not for field inspection. However the SEWG accepted to introduce one option based on the absence of symptoms observed in the crop and in its immediate vicinity (absence of inoculum)

9 - Risk management measures:

Is there a need to change the Risk management measure:

Yes

Proposed Risk management measure:

Pre-basic and Basic material:
(a) Field inspection of a representative sample of the plants in the crop and in its immediate vicinity at an appropriate time at which no symptoms are seen; or
(b) On a representative sample of seed not more than 0.1% of seeds are infected; or
(c) Seed treatment with an approved fungicide known to be effective against Ustilago tritici;
Field inspection and inspection of pre and post control plots may be used as an additional risk management measure to avoid any build-up of infection levels during the chain of propagation.

Certified material:
(a) Field inspection of a representative sample of the plants in the crop and in its immediate vicinity at an appropriate time at which no symptoms are seen; or
(b) On a representative sample of seed not more than [0.5-2%] of seeds are infected; or
(c) Seed treatment with an approved fungicide known to be effective against Ustilago tritici;
Field inspection and inspection of pre and post control plots may be used as an additional risk management measure to avoid any build-up of infection levels during the chain of propagation.

Justification (if necessary):

Experts did not agree on the threshold for certified material. This point need to be re-discussed at EU level.

3 - Is the pest already listed in a PM4 standard on the concerned host plant?

No

Conclusion:

Evaluation continues

4 - Are the listed plants for planting the main* pathway for the "pest/host/intended use" combination? (*: significant compared to others):

Yes

Conclusion:

Candidate

Justification:

Ustilago tritici (U. segetum var. tritici [and U. nuda]) causes loose smut of wheat. Infection is seed-borne within the seed. The spores of Ustilago tritici germinate on the ovary of a flowering plant and hyphae penetrate the ovary wall and grow towards the developing scutellum and embryo and remain dormant in these tissues until the seed starts to germinate. Seed is therefore a pathway. Infected seeds give rise to systemically infected plants and diseased ears are visible directly after heading. The black spores are released between glumes and broken-down grains, and are blown by the wind to infect neighbouring healthy ears (EPPO, 1997). Seed certification and seed treatment are very effective in controlling the disease, which is now practically unknown in intensive cereal cultivation in Europe. If untreated farmer-saved seed is sown, however, these diseases reappear (EPPO, 1997).
The directive 66/402 has a requirement for the seed producing crop that Ustilaginaceae shall be at the lowest possible level, but no seed-testing requirements are given. There is not a seed test by embryo extraction described by ISTA.
Volunteer plants grown from spilt contaminated seed from the previous year could in theory act as a disease source but this appears to be very rare because no references to this could be found. It is concluded seed can be considered as a significant pathway for the pest.

5 - Economic impact:

Are there documented reports of any economic impact on the host?

Yes

Justification:

Durum wheats (T. durum) are generally more susceptible than T. aestivum and in Canada the percentage of fields affected varied from 45% in 1994 to 78% in 1995, with the mean level of infected durum wheat plants per field ranging from <0.1 to 0.4%. (Thomas and Menzies, 1997). Loose smut disease of wheat in Canada, caused by Ustilago tritici, causes significant economic losses on both durum and bread wheats (Randhawa et al., 2009). In Morocco the pest was found in a survey on durum wheat but prevalence (% of contaminated fields) and severity varied from year to year (Ramdami & Ibriz, 2000).

What is the likely economic impact of the pest irrespective of its infestation source in the absence of phytosanitary measures? (= official measures)

Medium

Is the economic impact due to the presence of the pest on the named host plant for planting, acceptable to the propagation and end user sectors concerned?

No

Conclusion:

Candidate

Justification:

Yield losses are in proportion to the percentage of infected heads in the crop. Generally losses are low 1% but can be as high as 30%. Teliospores from infected ears can infect ovaries of health plants, re-establishing the disease in the next generation of seed produced. Infected seed are otherwise normal, visibly unaltered and fully germinable (Compendium of wheat diseases and pests,2010). Potential for the disease to multiply within a few years is great.

6 - Are there feasible and effective measures available to prevent the presence of the pest on the plants for planting at an incidence above a certain threshold (including zero) to avoid an unacceptable economic impact as regards the relevant host plants?

Yes

Conclusion:

candidate

Justification:

Control through standards for field inspection and seed, use of less susceptible varieties, and mostly through systemic seed treatment fungicides (e.g. tebuconazole, triticonazole, prothioconazole). These fungicides are not allowable for organic farming (management through testing and field inspections).

7- Is the quality of the data sufficient to recommend the pest to be listed as a RNQP?

Yes

Conclusion:

Candidate

Justification:

CONCLUSION ON THE STATUS:

Recommended for listing as an RNQP, based on data.

8 - Tolerance level:

Is there a need to change the Tolerance level:

Yes

Proposed Tolerance levels:

A tolerance (0.1% of seeds infected) for Pre-basic and Basic material (alternative option: absence of symptoms in the crop and its immediate vicinity), a tolerance (0.5 to 2% of seeds infected – no consensus within the SEWG) for certified material, with alternative risk management measures.

Justification (if necessary):

Relative importance of field inspection and sample testing was discussed by the SEWG. The SEWG agreed that field inspection, for this pest, will only show the level of presence of the pest in the planted material and not in the final seed lot. The SEWG agreed with the definition of a threshold for seeds and not for field inspection. However the SEWG accepted to introduce one option based on the absence of symptoms observed in the crop and in its immediate vicinity (absence of inoculum)

9 - Risk management measures:

Is there a need to change the Risk management measure:

Yes

Proposed Risk management measure:

Pre-basic and Basic material:
(a) Field inspection of a representative sample of the plants in the crop and in its immediate vicinity at an appropriate time at which no symptoms are seen; or
(b) On a representative sample of seed not more than 0.1% of seeds are infected; or
(c) Seed treatment with an approved fungicide known to be effective against Ustilago tritici;
Field inspection and inspection of pre and post control plots may be used as an additional risk management measure to avoid any build-up of infection levels during the chain of propagation.

Certified material:
(a) Field inspection of a representative sample of the plants in the crop and in its immediate vicinity at an appropriate time at which no symptoms are seen; or
(b) On a representative sample of seed not more than [0.5-2%] of seeds are infected; or
(c) Seed treatment with an approved fungicide known to be effective against Ustilago tritici;
Field inspection and inspection of pre and post control plots may be used as an additional risk management measure to avoid any build-up of infection levels during the chain of propagation.

Justification (if necessary):

Experts did not agree on the threshold for certified material. This point need to be re-discussed at EU level.

3 - Is the pest already listed in a PM4 standard on the concerned host plant?

No

Conclusion:

Evaluation continues

4 - Are the listed plants for planting the main* pathway for the "pest/host/intended use" combination? (*: significant compared to others):

No

Conclusion:

Not candidate

Justification:

No records of U.tritici (U. segetum var. tritici) [or U. nuda] could be found infecting Spelt wheat (T. spelta). Therefore it is considered not to be a host and therefore seed for planting is not a pathway.